A chimney meeting the roofline, where flashing seals the joint.
Flashing is the system of metal pieces that seals the joint where a chimney passes through the roof. It is not one part but a set — base flashing along the roof surface, step flashing woven into the shingles along the sides, and counter-flashing let into the masonry above — all working together to direct water away from the gap between the chimney and the roof. That gap is a natural weak point, and flashing is what keeps it watertight.
When flashing fails, water runs down the chimney and enters right at the roofline, often showing up as a stain on the ceiling near the chimney. Because that is also where several other leaks can appear, flashing has to be considered alongside the crown, cap, and masonry when tracing a leak. This page explains how flashing works, how it fails, and how the source of a roofline leak is narrowed down.
Signs of a flashing problem
- A ceiling stain or damp spot near the chimney, especially after rain.
- Visible rust, lifted, or separated metal where the chimney meets the roof.
- Cracked or failed sealant along the flashing lines.
- Flashing that was replaced with a smear of roofing tar as a temporary patch.
- Water intrusion that appears during wind-driven rain but not light rain.
Tar is a warning sign, not a repair
A common "fix" for flashing leaks is a heavy coat of roofing tar or sealant. It may slow a leak briefly, but it cracks, traps moisture, and hides the real condition of the flashing underneath. When we see a tarred-over joint, we treat it as a sign the flashing needs a real look, not proof that the problem was solved.
How the entry point is traced
Water is deceptive: it can enter at the roofline and travel along framing before appearing on a ceiling several feet away, which is why "the stain is near the chimney" does not by itself prove the flashing is the culprit. We look at the timing and pattern of the leak, the condition of the flashing, the crown and cap above, and the masonry, and we rule causes in or out rather than assuming. Sometimes the answer is the flashing; sometimes the flashing is fine and the water is coming from the crown or a cracked joint above it. (Our article on chimney leak vs. roof leak walks through this in more detail.)
Repair options
Depending on the findings, flashing work may involve resealing and securing existing flashing that is fundamentally sound, or replacing failed flashing with a properly installed system — base, step, and counter-flashing done correctly rather than patched. Where the leak turns out to be coming from elsewhere, we point you to the right fix rather than replacing flashing that was not the problem.
What changes the scope
Roof pitch and access, the roofing material, how the existing flashing was installed, and whether the leak has caused other damage all affect the work. Flashing that ties into masonry counter-flashing is more involved than a simple reseal. We assess before quoting.
Act on a roofline leak before it spreads
Water entering at the roofline does not just stain a ceiling — it can reach framing, insulation, and the chimney structure. A flashing leak is worth diagnosing and fixing promptly, before the hidden damage grows.
Why flashing is worth doing right, not fast
Flashing is one of the most commonly botched details on a roof, precisely because it is fiddly and mostly hidden once shingles and siding are in place. A proper job weaves step flashing into the courses of shingles along the sides of the chimney, ties counter-flashing into the masonry above so water cannot get behind it, and seals the base — all so that water is directed over the top of each layer and off the roof. Shortcuts, like relying on a bead of caulk or a coat of tar instead of correctly layered metal, tend to fail within a few seasons.
In a climate with frequent wind-driven rain, the stakes are higher, because water is not just falling straight down — it is being pushed sideways and upward against the joint. Flashing that would shrug off a gentle rain can let wind-driven water in if it was not installed to handle that force. When we address flashing, we treat it as a system that has to keep water out under real South Florida storm conditions, not just on a calm day, and we would rather do it correctly once than patch it repeatedly.
Flashing repair across South Florida
We diagnose and repair chimney flashing in West Palm Beach, Delray Beach, Boca Raton, and surrounding communities, where wind-driven rain makes a sound roof-to-chimney joint especially important. Call (561) 556-2104 to have a roofline leak traced.